Package tying machines are well known in the prior art exemplified by U.S. Pat. Nos. 1,606,290; 1,994,453; 2,371,024 and others. Such prior art machines feature a constantly operating electric drive motor for the tying mechanism and intervening gearing including a mechanical clutch under control of a machine operator through a foot treadle. The mechanical clutch is only engaged when the operator depresses the treadle to start a package tying cycle of operation, as fully described in the above-noted prior patents. When the cycle of operation is completed, the clutch is automatically disengaged by driven release means to condition the machine for the next tying cycle.
A serious safety hazard arises with these prior art machines if someone depresses the foot treadle while the machine is idle and the electric drive motor is turned off. Such action will engage the mechanical clutch and when the electric drive motor is subsequently started up, the twine tying mechanism is instantly activated and could injure the operator or anyone else whose hands or arms might be at that moment in the path of the rapidly moving wrapping arm of the machine.
The present invention has arisen as a direct result of the necessity to deal with the above safety hazard in a completely effective, simple and economic manner, and in this sense the invention is an improvement on the known prior art. The invention completely solves the safety problem without any mechanical alteration of the machine structure which is extremely satisfactory for its intended purpose of tying bundles or packages of twine. More particularly, the invention solves the problem by means of a simplified and economical electrical motor control means which forms a compact attachment unit on the machine near the electric motor.
By means of this small motor control attachment, the mode of operation of the machine at start-up is modified to fully overcome the safety problem without any structural changes in the machine mechanism. The normal package tying mode of operation of the machine remains unaltered.